The present invention relates to an adjustment control system in an adjustment mechanism for maintaining the quality of images produced by an image forming apparatus, such as an analog copying machine, a digital copying machine, a facsimile machine, and a laser printer.
An image forming apparatus, for example, an analog copying machine comprises an optical unit and a process unit. The optical unit reads an image on a document placed on a document table formed of glass. The process unit forms a developer image according to the image read out by the optical unit and transfers the image onto a recording medium such as a sheet paper.
In the copying machine, a resolution that can finally been obtained for a photocopy image depends on a resolution of exposure on a photoconductive drum and faithful-reproductivity of electrophotography processing for the exposure image.
For example, in an image forming apparatus, there occurs a case where photocopied objects produced by the same copying machine from the same original sheet material have densities differing from each other. The image density of an electrophotograph varies depending upon influence of variation and deterioration in image-forming conditions according to environmental and aging factors. Needless to say for analog copying machines, but also for other multigradation printers and digital copying machines, it is important to minimize the variation in the image density and to thereby stabilize the image density so that the quality of images can be maintained. Particularly, for color images, the image density influences not only density-reproductivity, but also color-reproductivity, therefore, it can be the that the stabilization in the image density is an indispensable conditional requirement.
Under these circumstances, conventional methods perform feedback control. The feedback control allows multiple test patterns to be formed on an image-carrier, detects the densities of the images, thereby grasps the variation in gradation characteristics, and repeats adjustment of operation sections in an image-forming section and determination for the quality (goodness or badness). In the control, the amounts of operations corresponding to control amount deviations are computed according to lookup tables preliminary created. The contents of the lookup tables are created offline. To describe the tables, a variety of experiments must be carried out to grasp characteristics (amounts of operations-corresponding to control amounts) of adjustment objects. The creation therefore requires much manpower and time.
In multi-input and multi-output systems, generally, the individual dependence relationships between inputs and outputs are not independent of each other. Therefore, description of the input-output relation-ships into the lookup tables requires lookup tables corresponding to the number of dimensions of the number of the inputs and the outputs. A system that handles a large number of dimensions therefore requires a large memory capacity for storing the tables; and accordingly, it requires a very large number of identification tasks All to be performed therefor. In addition, there are cases the aforementioned relationships are not suitable to an intended apparatus because of nonlinear characteristics, difference between the produces, reproductivity, and aged deteriorations. The employment of the feedback control allows the method to be practicable even in a case where the identification is incomplete to a certain extent. In this case, however, the number of converging operations and control time, before acceptance conditions of the quality determination is satisfied, is resultantly increased by the deviations from the characteristics of the apparatus that has processed the identification tasks.
As described above, in most cases where the multiple adjustment portions exist, adjustment portions have the dependence relationship with each other. This causes a phenomenon such as that, when one adjustment portion is adjusted in consideration of one adjustment amount, other multiple adjustment amounts are caused to vary; and when another adjustment portion is then operated for compensation therefor, a different characteristics amount is caused to vary. Thus, the method still arises problems in that the optimum adjustment is difficult and the efficiency of adjustment significantly decreases.
Jpn. Pat. Appln. KOKAI Publication No. 11-258873 discloses an adjustment control system that employs a rule-generating method, a feedback control method, and an adjustment control system. The rule-generating method generates desired adjusting rules according to the aforementioned various dependence relationships. The feedback control method repeats detection, determination, and scanning until a control amount deviation is adjusted to be within a given tolerance. This system combines the rule-generating method and the feedback control method, thereby successively detects the sensitivity, and further uses the adaptive-control method that determines the adjusting operation amount according to a result of the aforementioned checking for the density.
Adjustment-control systems as described above are required to implement reduction in the number of the control operations required for adjustment convergence and to implement further reduction in control time. For example, in an image forming apparatus, in a case where the density of a test pattern is measured, and the measurement is used as a control amount, developer consumption and apparatus-unusable time are required to be reduced as much as possible; and also, time required for the adjustment operation at an actual control site is required to be reduced as much as possible.
To comply with these requirements, Jpn. Pat. Appln. KOAKI Publication No. 2000-089525 proposes an adjustment control system that employs a so-called learning-control method and the above-described adaptive-control method. The learning-control method stores the relationships between individual control amounts and the operation amounts as successfully experienced instances so as to be used in subsequent control operations. The proposed system selectively executes the learning-control method and the adaptive-control method, and thereby, determines the operation amount. In addition, the proposed adjustment control system does not require the development of the lookup tables as described above, thereby allowing implementation of reduction of manpower, securement of adjustment convergence, and improvement in convergence efficiency.
However, the described adjustment control system, which selectively executes the adaptive-control method and the learning-control method, causes cases where the convergence is difficult, and defects such as overshoot occur when the system stores inappropriate learning data because of aged deteriorations and an abnormal state of the adjustment-object system. These defects repeatedly occur in subsequent adjusting operations.
The present invention has been contrived in consideration of the above circumstances and its object is to provide an adjustment control system which prevents occurrence of problems making convergence and the like in control operations to be difficult and which can efficiently perform an optimum adjustment.
To achieve the above, an adjustment control system for an image forming apparatus comprises detecting means for detecting individual control amounts; deviation computing means for computing a plurality of control amount deviations in accordance with the control amounts detected by the detecting means and a predetermined target value; deciding means for deciding whether or not the individual control amount deviations are within a predetermined tolerance; operation amount determining means for determining an operation amount for compensating each of the plurality of control amount deviations when at least one of the control amount deviations is determined by the detecting means to be out of the predetermined tolerance; a plurality of operating means for compensating the control amounts by performing operation by the determined operation amount; and a processing step control section for executing adjustment control that repeats the detection of the control amounts, the decision, the determination of the operation amounts, and the operation of the operating means until the control amount deviations computed are converged into the predetermined tolerance.
The operation amount determining means comprises an adaptive control section for executing adaptive control, which comprises operation selecting means for selecting the operating means for adjusting objective control amount deviations that are out of the predetermined tolerance according to a preliminarily provided adjustment rule, sensitivity detecting means for performing trial operations by a predetermined amount for the operating means selected and for thereby detecting the sensitivities of the control amount deviations which vary depending on the operation amount of the operating means, and first operation amount computing means for determining the operation amount according to the sensitivities detected for the operating means for reducing the objective control amount deviations; first storing means for storing control amount deviations and the operation amounts corresponding thereto on a basis of the detection and operation in a period when adjustment of the objective control amount deviations is started and the objective control amount deviations are adjusted to be within the tolerance; second storing means for computing the sum of the operation amounts which correspond to the control amounts in each compensation operation and stored in the first storing means and for storing the sum of the operation amounts as learning data when all the control amount deviations are adjusted to be within the tolerance; a learning control section comprising second operation amount computing means for determining the operation amount for the operating means according to the learning data stored in the second storing means and for executing a learning control method; determining means for determining whether or not learning data corresponding to the control amount deviations is stored in the second storing means; first control-method selecting means for determining the operation amount by selecting the adaptive control section when no corresponding learning data is determined by the determining means to exist and for determining the operation amount by selecting the learning control section when corresponding learning data is determined by the determining means to exist; and switching means for switching to adaptive control by the adaptive control section when a control amount deviation identical to the control amount deviation stored in the first storing means is computed by the deviation computing means during the execution of the learning control by the learning control section.
According to another aspect of the present invention, an adjustment control system for an image forming apparatus comprises detecting means for detecting individual control amounts; deviation computing means for computing a plurality of control amount deviations according to the control amounts detected by the detecting means and a predetermined target value; deciding means for deciding whether or not the individual control amount deviations are within a predetermined tolerance; operation amount determining means for determining an operation amount for compensating each of the plurality of control amount deviations when at least one of the control amount deviations is determined by the deciding means to be out of the predetermined tolerance; a plurality of operating means for compensating for the control amounts by performing operation by the operation amount determined; and a processing step controlling section for executing adjustment control that repeats the detection of the control amounts, the decision, the determination of the operation amounts, and the operation of the operating means until the control amount deviations computed are converged into the predetermined tolerance.
The operation amount determining means comprises an adaptive control section for executing adaptive control, which comprises operation selecting means for selecting the operating means for adjusting objective control amount deviations that are out of the predetermined tolerance according to a preliminarily provided adjustment rule, sensitivity detecting means for performing trial operations by a predetermined amount for the operating means selected and for thereby detecting the sensitivities of the control amount deviations which vary depending on the operation amount of the operating means, and first operation amount computing means for determining the operation amount according to the sensitivities detected for the operating means for reducing the objective control amount deviations; first storing means for storing control amount deviations and the operation amounts corresponding thereto on a basis of the detection and operation in a period when adjustment of the objective control amount deviations is started and the objective control amount deviations are adjusted to be within the tolerance; second storing means for computing the sum of the operation amounts which correspond to the control amounts in each compensation operation and stored in the first storing means and for storing the sum of the operation amounts as learning data when all the control amount deviations are adjusted to be within the tolerance; a learning control section comprising second operation amount computing means for determining the operation amount for the operating means according to the learning data stored in the second storing means and for executing a learning control method; determining means for determining whether or not learning data corresponding to the control amount deviations is stored in the second storing means; first control-method selecting means for determining the operation amount by selecting the adaptive control section when no corresponding learning data is determined by the determining means to exist and for determining the operation amount by selecting the learning control section when corresponding learning data is determined by the determining means to exist; and switching means for switching to the adaptive control by the adaptive control section when a control amount deviation is not converged into the predetermined tolerance as a result of the execution of the learning control by the learning control section.
In the above aspect of the invention, the adjustment control system comprise learning-data deleting means for deleting learning data used in the learning control when the learning control is switched by the switching means to the adaptive control by the adaptive control section.
Furthermore, according to the adjustment control system of the present invention, the operation amount determining means comprises an adaptive control section for executing adaptive control, which comprises operation selecting means for selecting the operating means for adjusting objective control amount deviations that are out of the predetermined tolerance according to preliminarily provided adjustment rule, sensitivity detecting means for performing trial operations by a predetermined amount for the operating means selected and for thereby detecting the sensitivities of the control amount deviations which vary depending on the operation amount of the operating means, and first operation amount computing means for determining the operation amount according to the sensitivities detected for the operating means for reducing the objective control amount deviations; first storing means for storing control amount deviations and the operation amounts corresponding thereto on a basis of the detection and operation in a period when adjustment of the objective control amount deviations is started and the objective control amount deviations are adjusted to be within the tolerance; second storing means for computing the sum of the operation amounts which correspond to the control amounts in each compensation operation and stored in the first storing means and for storing the sum of the operation amounts as learning data when all the control amount deviations are adjusted to be within the tolerance; a learning control section comprising second operation amount computing means for determining the operation amount for the operating means according to the learning data stored in the second storing means and for executing a learning control method; determining means for determining whether or not learning data corresponding to the control amount deviations is stored in the second storing means; a control method selecting means for determining the operation amount by selecting the adaptive control section when no corresponding learning data is determined by the determining means to exist and for determining the operation amount by selecting the learning control section when corresponding learning data is determined by the determining means to exist; and learning-data deleting means for deleting learning data used in the learning control when the control amount deviations satisfy predetermined adjustment control completion conditions before the control amount deviations are converged into the predetermined tolerance as a result of execution of the learning control by the learning control section, the adjustment control completion conditions including a conditional case where the operation amount is out of a predetermined limit value and a conditional case where the number of operations of the operating means in the adjustment control reaches a predetermined maximum number of control operations.
In the above aspect of the invention, the adjustment control system may also comprise an initial condition setting means for setting initial conditions and also for clearing the data stored in the method selection storing means when the adjustment control is started, and a retry means for allowing the initial condition setting means to clear data representing the initial conditions and the data in the method selection storing means and for allowing the adaptive control section to re-execute the adaptive control.
According to the adjustment control system configured as described above for use for the image forming apparatus, a control system can be configured such that the manpower for designing the controlling unit is reduced, and in addition, requirements for the difference between produces and long-term aged deteriorations of the control objects can be autonomously satisfied. Also, in an inexperienced state, the control methods such as the adaptive-control method that ensures the convergence quality and the learning-control method can be combined with each other. According to the combination, the sensitivity is checked successively or with appropriate timing, the operation amounts are thereby determined, cases where the convergence operations are completed are learned as successfully experienced instances. In a case similar to the previous operations, the knowledge obtained by the learning can be used; therefore, the number of converging operations can be reduced. In execution of the learning-control method, when the convergence for control amount deviations is difficult or when overshoot is caused, the method can be switched to the adaptive-control method, thereby allowing the quality of the convergence in the control to be assured. Also, deletion of unnecessary learning data prevents recurrence of defects such as overshoot, thereby allowing reliability to be improved.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.